To sense the rotary or angular position of a rotating mechanical part, it is necessary to couple the rotating part to a rotary sensor. For example, a grader type work vehicle includes front and rear wheels which support a generally longitudinal frame. The frame member provides support for a rotatable working blade. A rotary motor controls the rotary position of the blade. An electrical sensor senses the rotary position or angle of the blade. Any mechanical hysteresis between the rotating blade and the sensor will have a negative effect on the accuracy of the blade rotation system. In such a configuration, it is desirable to use a coupler that does not allow this type of hysteresis.